Continuous on-board diagnostic lubricant monitoring system and method

ABSTRACT

A continuous on-board diagnostic lubricant monitoring system and method evaluates lubricant quality and detects incipient lubricant failure due to contamination by measuring physical characteristics of the lubricant itself. The lubrication system ( 1 ) employs a diagnostic cell ( 27 ) which samples engine lubricant (EL) from an engine ( 2 ), and exposes the samples to sensors ( 28 ) which measure its physical characteristics. The senors ( 28 ) preferably include a permittivity sensor, a viscosity sensor, and a temperature sensor. Diagnostic testing based on the measurements can be carried out on-board via a controller ( 30 ) running selected algorithms or processes. A time to condemning limit for the lubricant, i.e., the time until the lubricant has degraded to given quality level, is calculated based on permittivity data received by the controller ( 30 ) from the sensors ( 28 ). Likewise, a time to condemning limit is calculated based on viscosity data. Based on the permittivity and temperature data, the controller ( 30 ) is able to detect incipient failure of the lubricant due to water or coolant contamination. Additionally, based on the monitored lubricant viscosity, the controller ( 30 ) is able to detect fuel contamination. In this manner, a superior lubricant monitoring system and method is achieved which is particularly applicable to railroad locomotives, mining machinery, and other off-highway vehicles.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to the art of oil and/or lubricantdiagnostics. It finds particular application in conjunction with dieselengines such as those employed in off-highway vehicles, e.g., railroadlocomotives, mining vehicles and machinery, etc. It will be describedwith particular reference thereto. However, it is to be appreciated thatthe present invention is also amenable to other internal combustionengines and the like which employ lubrication systems for variousapplications, be it off-highway applications, on-highway applications,or otherwise.

[0002] Maintenance of engine lubricant quality is essential to theproper operation and long service life of an internal combustion engine.A responsibility of the engine operator or maintenance personnel is toperiodically check the lubricant and, if needed, add an appropriateamount of fresh lubricant or change the lubricant entirely to maintainthe lubricant in the engine at a desired quality level. As used herein,the term “fresh lubricant” includes a base lubricant (e.g., a naturaloil, a synthetic oil, or the like) containing desired quantities andtypes of lubricant additives or adjuncts.

[0003] In general, the quality of the lubricant in an engine degradeswith engine use. Lubricant degradation occurs due to depletion oflubricant additives that perform specific functions such as controlviscosity, reduce wear, increase lubricity, minimize deposits, preventoxidation, and other desirable features. Lubricant degradation can alsooccur by the ingestion of foreign materials into the lubricant such asdirt from the surrounding environment, wear materials from the enginesthat occur as part of the natural operating process, and blow-by fromthe combustion process. Lubricant degradation can also occur due to abreak-down of the base stock of the lubricant. In the extreme case fuelor water/coolant contamination of the lubricant can cause lubricantdegradation.

[0004] Two ways of improving the quality of the engine lubricant is toperiodically remove some or all of the engine lubricant and replace itwith fresh lubricant. Also, in most cases filters are used to removeforeign materials above a certain size from the engine lubricant.Various systems have been proposed for periodically removing a givenquantity of lubricant from the engine and either storing the lubricantuntil it can properly be disposed of, or in the case of a diesel engine,optionally periodically injecting the lubricant into the fuel tank wherethe lubricant is mixed with the fuel and then burned in the engine alongwith the fuel. Also, it is generally known to provide such systems withautomatic lubricant level sensing devices which maintain the properlevel of lubricant in the engine.

[0005] In some systems, a given quantity of the engine lubricant isremoved at preset time intervals based on engine usage factors. Inothers, small increments of engine lubricant are periodically removedand substantially simultaneously replaced with correspondingly smallincrements of fresh lubricant. In still others, a given amount of enginelubricant is periodically removed based on sensors that measuredifferent operating variables of the engine such as the level,temperature and/or pressure of the lubricant within the engine, thenumber of engine starts or crank shaft revolutions, the length of timethe engine has been in motion and at rest, engine temperature, fuelconsumption, etc. See, e.g., U.S. Pat. No. 5,749,339 to Graham, et al.

[0006] However, many previously developed lubrication systems arecharacterized by certain limitations and/or drawbacks. For example,systems that employ a set periodic maintenance schedule can have lessthan optimized engine operation time due to unnecessary maintenance downtime. Likewise, systems that employ a maintenance schedule based onengine operation and/or operating conditions can also experience thesame problem insomuch as these factors, while perhaps indicative, do notdirectly reflect the lubricant quality. Therefore, estimates of thelubricant's amount of degradation are imprecise and maintenance orlubricant exchanges may be prematurely scheduled. In addition tounnecessary down time, prematurely scheduled maintenance or lubricantexchanges result in unnecessary lubricant consumption. On the otherhand, late maintenance or lubrication exchange is even less desirableinsomuch as it can result in unnecessary engine wear, reducing enginelife, and possible engine failure. Consequently, the previouslydeveloped lubrication systems tended to error on the side of prematuremaintenance and/or premature lubrication exchange.

[0007] Moreover, the previously developed systems did not account for ordetect conditions which may prompt lubricant failure, such as, e.g.,incipient failure detection (IFD) denoted by significant water/coolantcontamination and/or fuel contamination of the lubricant. Presetmaintenance schedules and maintenance schedules based on engineoperation and/or operating conditions do not anticipate lubricantfailure due to unexpected contamination.

[0008] Accordingly, there is a need for a system that more effectivelydetermines the condition and thus the quality of the engine lubricant,such that when the quality of the engine lubricant degrades apredetermined amount or incipient failure is detected, appropriatecorrective or otherwise responsive actions may be taken.

[0009] The present invention contemplates a new continuous on-boarddiagnostic lubricant monitoring system and method which at leastpartially overcomes the above-referenced problems and others.

SUMMARY OF THE INVENTION

[0010] In accordance with one aspect of the present invention, a methodof monitoring a lubricant is provided. The method includes the steps ofmeasuring the lubricant's temperature, and measuring the lubricant'spermittivity. After temperature dependence in the permittivity has beencompensated for, it is determined if the lubricant has been contaminatedby water or other coolant.

[0011] In accordance with a more limited aspect of the presentinvention, the method also includes determining a rate of change of thelubricant's permittivity for a first period of time, and determining arate of change of the lubricant's temperature for a second period oftime. The lubricant is then determined to be contaminated by a coolantif the rate of change of the lubricant's permittivity for the firstperiod of time is greater than a first threshold, and an absolute valueof the rate of change of the lubricant's temperature for the secondperiod of time is less than a second threshold.

[0012] In accordance with a more limited aspect of the presentinvention, the first and second periods of time are the same.

[0013] In accordance with a more limited aspect of the presentinvention, the method also includes determining a rate of change of thelubricant's temperature for a third period of time, where the thirdperiod of time is greater than the first and second periods of time. Inthis case, for a determination to be made that the lubricant iscontaminated by a coolant, it has to also be found that the rate ofchange of the lubricant's temperature for the third period of time isless than a third threshold

[0014] In accordance with a more limited aspect of the presentinvention, the method also includes selecting a minimum temperature fromthose used to determine the rate of change of the lubricant'stemperature for the second time period. In this case, for adetermination to be made that the lubricant is contaminated by acoolant, it has to also be found that the minimum temperature is greaterthan a threshold temperature.

[0015] In accordance with another aspect of the present invention, amethod of monitoring a lubricant includes obtaining, over time,permittivity data from measured permittivity values of the lubricant.Based on changes in the permittivity data over time, a rate ofdegradation of the lubricant's quality is determined, and an amount oftime until the lubricant reaches a set degraded quality level is furtherdetermined.

[0016] In accordance with a more limited aspect of the presentinvention, the method also includes determining if the lubricant hasbeen changed or topped-off by detecting changes in the permittivity datawhich exceed a threshold level.

[0017] In accordance with a more limited aspect of the presentinvention, the amount of time until the lubricant reaches the setdegraded quality level is given by:

(cond_limit−current_perm)/perm_slope

[0018] where, cond_limit represents a condemning limit defined by thelubricant's permittivity when the lubricant has reach the set degradedquality level; current_perm represents the lubricant's currentdetermined permittivity; and perm_slope represents the determined rateof degradation of the lubricant's quality based on changes in thepermittivity data.

[0019] In accordance with a more limited aspect of the presentinvention, the current determined permittivity of the lubricant is amedian of a plurality of most recently obtained permittivity data.

[0020] In accordance with another aspect of the present invention, alubrication system for an engine is provided. The lubrication systemincludes a lubricant, and a diagnostic cell which samples the lubricantfor diagnostic testing thereof. The diagnostic cell includes apermittivity sensor which monitors the lubricant's permittivity, and atemperature sensor which monitors the lubricant's temperature.

[0021] In accordance with a more limited aspect of the presentinvention, the diagnostic cell further includes a manifold in which thepermittivity and temperature sensors are mounted. The manifold isarranged such that sampled lubricant is selectively made to encounterthe permittivity and temperature sensors.

[0022] In accordance with a more limited aspect of the presentinvention, the lubrication system also includes a controller whichinterfaces with the diagnostic cell to carry out the diagnostic testing.The controller receives permittivity data from the permittivity sensorand temperature data from the temperature sensor.

[0023] In accordance with a more limited aspect of the presentinvention, the diagnostic testing carried out includes determining ifthe lubricant has been contaminated by a coolant.

[0024] In accordance with a more limited aspect of the presentinvention, the controller determines a rate of change of the lubricant'spermittivity for a first time period based on the permittivity data itreceives, and the controller determines a rate of change of thelubricant's temperature for a second time period based on thetemperature data it receives. The controller determines that thelubricant has been contaminated by a coolant if the rate of change ofthe lubricant's permittivity for the first time period is greater than afirst threshold and an absolute value of the rate of change of thelubricant's temperature for the second time period is less than a secondthreshold.

[0025] In accordance with a more limited aspect of the presentinvention, the controller further determines a rate of change of thelubricant's temperature for a third time period based on the temperaturedata it receives. The third time period is longer than the first andsecond time periods. For the controller to determine that the lubricanthas been contaminated by a coolant in this case, the controller has toalso find that the rate of change of the lubricant's permittivity forthe third time period is less than a third threshold.

[0026] In accordance with a more limited aspect of the presentinvention, the controller further determines a minimum lubricanttemperature for the second time period from the temperature data itreceives. For the controller to determine that the lubricant has beencontaminated by a coolant in this case, the controller has to also findthat the minimum lubricant temperature is greater than a thresholdtemperature.

[0027] In accordance with a more limited aspect of the presentinvention, the controller determines a time to condemning limit for thelubricant based on the permittivity data received. In accordance with amore limited aspect of the present invention, the time to condemninglimit is given by:

(cond_limit−current_perm)/perm_slope

[0028] where, cond_limit represents a condemning limit defined by thelubricant's permittivity when the lubricant has reach a selected levelof degradation; current_perm represents the lubricant's currentdetermined permittivity; and perm slope represents a rate of lubricantquality degradation as determined from the permittivity data.

[0029] In accordance with a more limited aspect of the presentinvention, the engine is either a railroad locomotive engine or a miningvehicle engine.

[0030] In accordance with another aspect of the present invention, amethod of monitoring a lubricant is provided. The method includesobtaining measurements of the lubricant's viscosity and temperature. Theviscosity measurements are then normalized based on the temperaturemeasurements such that the normalized viscosity measurements all relateto a common reference temperature. Finally, a condition of the lubricantis diagnosed based on the normalized viscosity measurements.

[0031] In accordance with a more limited aspect of the presentinvention, the diagnosis includes diagnosing fuel contamination andlubricant “shear down” of the lubricant based on the normalizedviscosity measurements.

[0032] In accordance with a more limited aspect of the presentinvention, the diagnosis includes distinguishing between differentdegrees of fuel contamination based on the normalized viscositymeasurements.

[0033] In accordance with a more limited aspect of the presentinvention, the method also includes determining, based on the normalizedviscosity measurements, a time to condemning limit for the lubricant dueto fuel contamination.

[0034] In accordance with a more limited aspect of the presentinvention, the diagnosis includes diagnosing quality degradation of thelubricant based on the normalized viscosity measurements.

[0035] In accordance with a more limited aspect of the presentinvention, the method also includes determining, based on the normalizedviscosity measurements, a time to condemning limit for the lubricant dueto quality degradation.

[0036] In accordance with a more limited aspect of the presentinvention, the method also includes determining, based on the normalizedviscosity measurements, a time to condemning limit for the lubricant.

[0037] In accordance with a more limited aspect of the presentinvention, the time to condemning limit is one of an upper viscositylimit under which it is desired that the lubricant's viscosity remain,or a lower viscosity limit over which it is desired that the lubricant'sviscosity remain.

[0038] In accordance with another aspect of the present invention, alubrication system for an engine includes a lubricant, and a diagnosticcell which samples the lubricant for diagnostic testing thereof. Thecell includes a viscosity sensor which monitors the lubricant'sviscosity, and a temperature sensor which monitors the lubricant'stemperature. It is this temperature sensor that is utilized to normalizethe viscosity measurement.

[0039] A controller interfaces with the diagnostic cell to carry out thediagnostic testing. The controller receives viscosity data from theviscosity sensor and temperature data from the temperature sensor. Theviscosity and temperature data is processed to diagnose a condition ofthe lubricant.

[0040] In accordance with a more limited aspect of the presentinvention, the condition diagnosed is one of fuel contamination of thelubricant, or quality degradation of the lubricant. In accordance with amore limited aspect of the present invention, the viscosity data and thetemperature data are processed to determine a time to condemning limitfor the lubricant.

[0041] In accordance with a more limited aspect of the presentinvention, the viscosity sensor is a dynamic (rotational) viscocometer.

[0042] In accordance with a more limited aspect of the presentinvention, the lubrication system also includes a data link whichtransfers data between the lubrication system and a site remote from thelubrication system.

[0043] In accordance with a more limited aspect of the presentinvention, the lubrication system also includes a manifold in which theviscosity and temperature sensors are mounted. The manifold is arrangedsuch that sampled lubricant is selectively made to encounter theviscosity and temperature sensors.

[0044] In accordance with a more limited aspect of the presentinvention, the lubrication system also includes indicating means forproviding a human perceivable indication of the condition of thelubricant.

[0045] In accordance with a more limited aspect of the presentinvention, the lubrication system also includes a storage device inwhich the viscosity and temperature data are saved.

[0046] In accordance with a more limited aspect of the presentinvention, the lubrication system also includes lubricant refreshingmeans for selectively carrying out one or more functions in response tothe diagnosed condition of the lubricant. The functions carried outinclude removing lubricant from the lubrication system, and/or addingfresh lubricant to the lubrication system.

[0047] In accordance with a more limited aspect of the presentinvention, the engine is a railroad locomotive engine, or a miningvehicle engine.

[0048] One advantage of the present invention is continuous on-boardmonitoring of engine lubricant quality.

[0049] Another advantage of the present invention is protection of theengine from excessive lubricant degradation and incipient lubricantfailure due to unexpected contamination.

[0050] Still another advantage of the present invention is improvedengine operation time. Another advantage of the present invention islubricant conservation.

[0051] Still further advantages and benefits of the present inventionwill become apparent to those of ordinary skill in the art upon readingand understanding the following detailed description of the preferredembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The invention may take form in various components andarrangements of components, and in various steps and arrangements ofsteps. The drawings are only for purposes of illustrating preferredembodiments and are not to be construed as limiting the invention.

[0053]FIG. 1 is a schematic illustration of a lubrication systememployed in accordance with aspects of the present invention in which aportion of a pressurized engine lubricant is shown being divertedthrough a flow path containing a diagnostic cell and then returned to anengine lubricant sump;

[0054]FIG. 2 is a schematic illustration of the system of FIG. 1 butshowing pressurized engine lubricant being diverted into a lubricantreservoir and then into an engine fuel tank, and fresh lubricant beingadded to the engine lubricant sump through a flow path downstream of thediagnostic cell;

[0055]FIG. 3 is a schematic illustration of a modified lubricationsystem employed in accordance with aspects the present invention inwhich pressurized engine lubricant is diverted directly to the enginefuel tank on command of a system controller;

[0056]FIG. 4 is a flow chart showing a process for detecting incipientlubrication failure due to water/coolant contamination in accordancewith aspects of the present invention;

[0057]FIG. 5 is a flow chart showing a process for determining alubricant's time to condemning limit base on permittivity monitoring inaccordance with aspects of the present invention; and,

[0058]FIG. 6 is a flow chart showing a process for lubrication diagnosisbased on viscosity monitoring in accordance with aspects of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059] Referring now in detail to the drawings, and initially to FIG. 1,there is schematically shown one preferred embodiment of an continuouson-board diagnostic lubricant monitoring system 1 in accordance with thepresent invention for maintaining the quality and level of lubricant EL(e.g., an oil including additives and base material) in an internalcombustion engine 2, which may for example be a diesel engine used topower a railroad locomotive. The engine 2 is schematically shown insection in FIG. 1 with the usual pistons 3, fuel injectors 4, and enginelubricant sump 5 containing the engine lubricant EL. Also, an enginedriven lubricant pump 7 is shown which, when driven by the engine 2,causes the engine lubricant EL to flow from the sump 5 through anexternal lubricant line 8 containing a filter 9 and onto the movingparts of the engine to minimize friction and wear. The engine lubricantEL then returns to the sump 5 for recirculation through the fluid line 8and onto the engine parts as before.

[0060] The lubricant EL within the engine sump 5 is typically nearatmospheric pressure, whereas the lubricant in the fluid line 8 externalto the engine 2 is at a significantly higher pressure, for example onthe order of 30 psi or greater.

[0061] Also shown in FIG. 1 is the fuel line 10 through which fuel F ispumped from a fuel tank 11 by a fuel pump 12 through a fuel filter 13and a meter 14 to the fuel injectors 4 of the engine during engineoperation. Depending on the throttle position of the engine, eachinjector 4 injects metered amounts of fuel into the combustion chambers16 at very high pressures. The excess fuel serves to cool the injectors4 and is returned to the fuel tank 11 through a common line 17containing a fuel meter 18. Preferably, level sensors 19, 20 areemployed in both the fuel tank 11 and engine sump 5 to roughly determinethe liquid volume in each of these reservoirs.

[0062] For determining and monitoring the quality of the enginelubricant EL, the system 1 includes a fluid conduit 25 connected to thehigh pressure engine lubricant line 8 upstream of the engine lubricantfilter 9. Conduit 25 contains a three-way valve 26 which, in the normal“off” state shown in FIG. 1, directs a portion of the pressurized enginelubricant EL through a diagnostic manifold or cell 27 containing aplurality of sensors 28 for measuring certain physical characteristicsof the engine lubricant EL, for example, the temperature, pressure,permittivity and/or viscosity of the engine lubricant EL. Downstream ofthe diagnostic cell 27 is another three-way valve 29 which, in thenormal “off” state, returns the portion of the engine lubricant passingthrough the diagnostic cell 27 to the engine lubricant sump 5 throughthe conduit 25.

[0063] The fluid conduit 25 is sized to restrict the rate of enginelubricant flow through the diagnostic cell 27 to a relatively smallamount, for example approximately three percent of the total flow outputof the engine lubricant pump 7, which is considered insignificant to theproper lubrication of the engine 2.

[0064] A system controller 30, comprising, e.g., a computer,microprocessor or the like, monitors the outputs from the sensors 28 inthe diagnostic cell 27 (and possibly others as described hereafter) todiagnose the engine lubricant EL, detect selected conditions, and/ordetermine the engine lubricant quality based on control algorithms. Inresponse to the diagnosis made, the condition detected, and/or thedetermined level of lubricant quality, desired actions can be taken.

[0065] In a preferred embodiment, for example, when the quality of theengine lubricant EL drops below a predetermined level as ascertained bythe controller 30, the controller periodically commands the valve 26 toredirect the diverted engine lubricant through another conduit 31 to alubricant reservoir 32 as schematically shown in FIG. 2 where the enginelubricant may be stored until otherwise disposed of. A meter 33 andfilter 34 are provided in the conduit 31 upstream of the lubricantreservoir 32 for metering and filtering the lubricant before enteringthe reservoir. Also, a level sensor 35 is preferably provided in thereservoir 32 for roughly determining the liquid volume in the reservoir32.

[0066] If the engine 2 is of a type such as a diesel engine that canburn a lubricant-fuel mixture, a fluid pump 36 may be provided withinthe engine lubricant reservoir 32 for pumping a predetermined amount ofthe engine lubricant within the reservoir through a conduit 37containing a flow meter 38 and into the common line 17 leading to thefuel tank 11 upon command by the system controller 30 as furtherschematically shown in FIG. 2.

[0067] Alternatively, the conduit 31 that receives the redirected enginelubricant from the engine upon command of the system controller 30 maybe connected directly to the common line 17 leading to the fuel tank 11as schematically shown in FIG. 3, thus eliminating the need for theengine lubricant reservoir 32 and associated pump 36, conduit 37 andflow meter 38. In that event, a further valve 39 is desirably providedin the conduit 31 which, when activated by the system controller 30,prevents the flow of engine lubricant through the conduit 31 to the fueltank 11 as a safety in the event the valve 26 should fail and the freshlubricant pump 43 (described hereafter) is not operating.

[0068] However, storing the engine lubricant EL in a reservoir 32 priorto adding the engine lubricant EL to the fuel tank 11 has the advantagethat periodic activation of the valve 26 to remove some of the enginelubricant EL from the engine 2 does not have to coincide with itsdeposit into the fuel tank 11 or fueling of the fuel tank 11. Also, theamount of engine lubricant EL that is removed from the engine 2 at anygiven time can be greater than the maximum amount that could be added tothe fuel tank 11 at that time without exceeding a predeterminedlubricant/fuel ratio for the particular engine 2.

[0069] In either case, the engine lubricant EL is preferably added tothe fuel tank 11 either in conjunction with the fueling of the fuel tank11 or as soon after fueling as possible to maximize the amount of enginelubricant EL that can be added to the fuel F without exceeding apredetermined lubricant/fuel ratio for the engine 2. Also, the enginelubricant EL is desirably added to the fuel tank 11 through the commonline 17 only while the engine 2 is operating so that the enginelubricant EL will be mixed with the warm, relatively rapidly flowingfuel F returning from the injectors 4 to the fuel tank 11.

[0070] The system 1 also includes a reservoir 40 containing freshlubricant FL for use in maintaining the desired quality and level ofengine lubricant EL within the engine lubricant sump 5. In a preferredembodiment, a sensor 41 is provided in the reservoir 40 for roughlydetermining the volume of fresh lubricant FL within the reservoir 40.The fresh lubricant reservoir 40 is desirably selectively connected tothe same conduit 25 through which the diverted engine lubricant EL isnormally recirculated back to the engine 2 by the three-way valve 29 inthe conduit 25 downstream of the diagnostic manifold or cell 27. Whencommanded by the system controller 30, the valve 29 moves to a positionblocking flow of engine lubricant EL from the diagnostic cell 27 andallowing fresh lubricant FL to be pumped from the fresh lubricantreservoir 40 by a pump 43 within the reservoir through a meter 44 intothe conduit 25 downstream of the diagnostic cell 27 and into the engine2 as schematically shown in FIGS. 2 and 3.

[0071] In operation, the system controller 30 monitors the sensors 28 inthe diagnostic cell 27, the level sensors 35 and 41 in the lubricantreservoirs 32 and 40, the flow meter 33 for measuring the redivertedflow of engine lubricant EL to the lubricant reservoir 32 or to the fueltank 11, and the flow meters 38 and 44 for measuring the outflows fromthe lubricant reservoirs 32 and 40. Also, the system controller 30 maybe used to monitor other components which include the lubricant levelsensor 20 in the engine lubricant sump 5, the fuel level sensor 19, andpossibly the fuel meters 14 and 18 as well as other sensors 50 mountedin conjunction with or on the engine 2, schematically shown in thedrawings, for measuring such engine parameters such as engine usagebased on one or more operating variables of the engine 2 or of theequipment powered by the engine 2 including the number of engine starts,engine running time, number of miles driven, amount of fuel F used sincethe last fresh lubricant addition, etc.

[0072] Based on the monitored sensors and/or components, the systemcontroller 30 determines when to activate the valve 26 to redirect aportion of the lubricant EL from the engine 2 to the lubricant reservoir32 (or directly to the engine fuel tank 11 if no lubricant reservoir isprovided), and when to activate the valve 29 and pump 43 in the freshlubricant reservoir 40 to transfer fresh lubricant FL to the engine sump5 to maintain the quality and level of the lubricant in the engine 2.Also based on monitored sensors and/or components, the system controller30 determines when and the amount of fuel F added to the engine fueltank 11 through a nozzle 51, schematically shown in FIG. 1, andactivates the pump 36 (if the engine lubricant reservoir 32 is includedin the system) to add filtered engine lubricant EL from the reservoir 32to the fuel tank 11 in an amount not to exceed a predeterminedlubricant/fuel ratio, or until the engine lubricant reservoir 32 isempty. As previously indicated, the engine lubricant EL is preferablyadded to the fuel tank 11 either in conjunction with the fueling or assoon thereafter as possible, but preferably only while the engine 2 isoperating so that the engine lubricant EL is mixed with the warm,rapidly flowing fuel F returning from the injectors 4 to the fuel tank11 through the common line 17.

[0073] Of course, if the system 1 does not include a engine lubricantreservoir 32, and the redirected engine lubricant EL is added directlyto the fuel tank 11 as schematically shown in FIG. 3, the systemcontroller 30 would preferably not activate the valve 26 to redirect theengine lubricant EL to the engine fuel tank 11 except in conjunctionwith the fueling or as soon after fueling as possible, and preferablyonly while the engine 2 is operating for the reasons previouslydescribed.

[0074] Also based on monitored sensors and/or components, the systemcontroller 30 determines when to activate the valve 29 for blocking theflow of diverted engine lubricant EL through the diagnostic cell 27 andthe pump 43 in the fresh lubricant reservoir 40 to transfer freshlubricant FL into the engine 2.

[0075] The system controller 30 optionally includes a display 52 thatallows visual output of the monitored sensors and/or components.Volatile and/or non-volatile on-board storage devices 58 (e.g., magneticstorage devices or disk drives, computer memory, etc.) are used tomaintain current and historical data logs or records of the measuredengine, system and lubricant characteristics.

[0076] The system controller 30 may also be used to keep track of theengine location via a Global Position Satellite (GPS) unit 55. Inaddition, the system controller 30 may be used to communicate the datathat it receives from the sensors and/or components and/or data from thestorage devices 58 to a remote site through a data link 56 such as asatellite communications modem, a cellular network, or the like.Depending on the data type, it is optionally communicated continuouslyto the remote site and/or at predetermined or selected periodicintervals. Additionally, specific data may be communicated immediatelyupon receiving a demand or request therefor from the remote site. Incertain circumstances, a data communication may be initiated by thesystem controller 30, e.g., when a condition is detected or diagnosismade indicative of incipient failure.

[0077] Note the various lubricant flow meters 33, 38 and 44 and fuelflow meters 14 and 18 would be redundant if the lubricant and fuel levelsensors 20, 35, 41 and 19 were highly accurate. However, in the usualcase, such level sensors only provide relatively rough measurements ofthe liquid volume in the sump 5, reservoirs 32 and 40 and tank 11, whichare sufficient to maintain proper lubricant level in the engine 2, tolimit the lubricant to fuel ratio in the fuel tank 11, to prevent theremoval of lubricant EL from the engine 2 if there is not sufficientfresh lubricant FL in the fresh lubricant reservoir 40 to replace theremoved amount, and to prevent the removal of lubricant EL from theengine 2 if there is not sufficient volume to receive the lubricant inthe lubricant reservoir 32.

[0078] With respect to the diagnostic cell 27, at least one of thesensors 28 incorporated therein is preferably a permittivity sensorwhich operates at a defined frequency. The permittivity measurementsobtained from the permittivity sensor are related to the amount ofgeneral polarized materials or species in the lubricant EL. Typically,the lubricant EL is characterized by a natural or synthetic oilincluding polar additives and non-polar base material. As the additivesdegrade, the polarity tends to increase. Additionally, as combustionby-products or water/moisture or coolant enter the lubrication system,the polarity also increases. In this manner then, incipient failure ofthe lubricant EL due to water or coolant contamination can be diagnosedin part by monitoring the permittivity of the lubricant EL.Additionally, a time to a condemning limit for the engine lubricant ELmay also be predicated on permittivity monitoring.

[0079] Permittivity is a temperature dependent characteristic of thelubricant EL. Accordingly, a temperature sensor (e.g., a thermocouple orthe like) is also preferably included among the sensors 28 incorporatedin the diagnostic cell 27 to take measurements of the engine lubricant'stemperature concurrently with each permittivity measurement.

[0080] Using the obtained permittivity measurements and the obtainedtemperature measurements, incipient failure of the engine lubricant ELdue to water leaks and it's time to condemning limit can be determinedor diagnosed. In response thereto, appropriated corrective or otheractions are optionally taken as desired, e.g., an engine shut-down maybe in order, engine servicing may be scheduled and/or performedincluding a lubrication change, fresh lubricant FL from the reservoir 40may be added, or used engine lubricant EL may be removed and routed tothe reservoir 32 if available. In this manner then, the engine isprotected from the hazards of lubricant failure and/or degradation whilemaximizing the engine's operation time between servicing.

[0081] Alternately, the calculations and/or algorithms (described below)are perform on-board by the system controller 30, or data is off-loadedvia the data link 56 to a remote site where the calculations areperformed, or some combination of both. In any event, the calculationresults, desired instructions or warnings based thereon, related data,and the like are preferably communicated to the engine operator,maintenance personnel or other interested parties, e.g., via the visualdisplay 52 or other like indicators. Where the calculations wherecarried out at least in part at the remote site, the results or otherdata are optionally up-loaded over the data link 56. Additionally, thedata, intermediate or final calculation results, related information andthe like are optionally stored on-board in one or more of the storagedevices 58.

[0082] The incipient failure determination or diagnosis due towater/coolant leaks or contamination is now described by way of example,with reference to FIG. 4 which is a box diagram illustrating the same.The incipient failure diagnostic process is alternately carried out viasoftware implementation, hardware implementation or a combination ofboth.

[0083] The incipient failure diagnosis due to a water/coolant leak orcontamination, which process is generally indicated by reference numeral100, begins at start box 102 where initialization takes place. Inaddition to optional system, sensor, or other fault checking and/orcalibration, initialization preferably includes the setting of certainparameters including thresholds and other values used in the incipientfailure diagnosis 100 such as, e.g., the parameters n1, n2, perm slopelimit, temp_slope1_limit, and temp_slope2_limit (described hereafter).Setting of the parameters may be predetermined and/or fixed and theirvalues optionally stored in one or more of the storage devices 58 orotherwise. Alternately, the parameter values are variable, and they maybe manually entered, supplied by the remote site, or otherwise selected.In one preferred embodiment, the parameter values are obtained from alook-up table or other like source based on the engine type, thelubrication type, and/or other like factors. In any event, the assignedparameter values are preferably based on historical observations anddata related to incipient failure of lubricants due to water/coolantleaks. Additionally, the assigned parameter values are preferably set tooptimally tune the incipient failure diagnosis 100 for specificapplications or circumstances.

[0084] The next step 104 is to acquire a set of measurements or data.The diagnostic process 100 is preferably a continually updated iterativeprocess with each iteration employing a set of data values representingthe most recent permittivity data and the most recent temperature data.Alternately, each data point may represent an individual measurement oran average or otherwise weighted measurement taken over time. In apreferred embodiment, the acquired data is “minute data.” Minute data isthe result of a number of measurements taken at intervals (e.g., 1second intervals) over the period of 1 minute, which measurements areaveraged to obtain the data value for that minute. Minute data forconsecutive 1 minute periods is then acquired approximately concurrentlyfor both permittivity and temperature. A complete data set for any onegiven iteration preferably includes n1 of the most recent permittivityvalues and n2 of the most recent temperature values, where n1 and n2 areintegers greater than zero and n2>n1. In a preferred embodiment, forexample, n1=5 and n2=20.

[0085] As it is acquired, the data may be stored in one or more of thestorage devices 58. Once the first complete set of data has beenacquired, the diagnostic process 100 may continue. Thereafter,subsequent iterations are carried out after each acquisition of the nextpermittivity value and its corresponding temperature value. That is,with each update the oldest data values used in the immediatelypreceding iteration are now disregarded, the remaining other data valuesare shifted or re-indexed accordingly, and the newly acquired datavalues placed into the current iteration positions. In this manner then,when “minute data” is employed, the incipient failure diagnosis isupdated every minute after the first iteration. Optionally, to conservestorage room, only the n1 most recently acquired permittivity values andthe n2 most recently acquired temperature values are saved, and witheach update the oldest of both are discarded, deleted or written over.

[0086] At the next step 106, the acquired set of data undergoesprocessing and/or calculations are made based thereon to determinecertain characteristics of the engine lubricant EL. In particular, arate of change of the lubricant's permittivity, a “short” term rate ofchange of the lubricant's temperature, and a “long” term rate of changeof the lubricant's temperature are preferably determined. The “long” and“short” terms are relative to one another, with the short termpreferably relating to the time in which the n1 most recent data valueswere acquired, and the long term preferably relating to the time inwhich the n2 most recent data values were acquired. For exemplarypurposes herein, the rate of change of the lubricant's permittivity isnominally termed “slope1,” the short term rate of change of thelubricant's temperature is nominally termed “slope2,” and the long termrate of change of the lubricant's temperature is nominally termed“slope3.”

[0087] In a preferred embodiment, the data used for determining orcalculating slope1 are the n1 most recently acquired permittivityvalues, the data used for determining slope2 are the n1 most recentlyacquired temperature values, and the data used for determining slope3are the n2 most recently acquired temperature values. Each of the threecharacteristics are preferably determined or calculated by initiallycentering the respective data, i.e., subtracting the mean from eachvalue. The centered values for each calculation are then regressed,preferably, using a least-squares fit or other linear regression. Wherethe data was acquired at regular intervals, the centered values areregressed against integer values representing the relative order of thedata values' acquisition. Finally, the slope of each regression is takenas the corresponding value for slope1, slope2, and slope3, respectively.

[0088] In a preferred embodiment, the algorithm or calculation used todetermine each of slope1, slope2, and slope3 is mathematically given by:$\begin{matrix}{{{{slope}\quad N} = \frac{{n{\sum\limits_{i = 1}^{n}{x_{i}y_{i}}}} - {\underset{i = 1}{\overset{n}{\sum\quad}}x_{i}{\sum\limits_{i = 1}^{n}y_{i}}}}{{n{\sum\limits_{i = 1}^{n}x_{i}^{2}}} - {n\left\lbrack {\sum\limits_{i = 1}^{n}x_{i}} \right\rbrack}^{2}}},} & (1)\end{matrix}$

[0089] where slopeN represents slope1, slope2, or slope3 for therespective calculations, n represents the total number of data points ineach of the respective calculations (i.e., n=n1 for the calculations ofslope1 and slope2, and n=n2 for the calculation of slope3), x_(i)represents the integers from 1 to n, and y_(i) represents the respectivedata values for each of the calculations (i.e., y_(i) represents theacquired permittivity data for the calculation of slope1, and y_(i)represents the acquired temperature data for the calculations of slope2and slope3).

[0090] At determination step 108, after the engine lubricantcharacteristics (i.e., slope1, slope2, and slope3) have been evaluated,it is determined whether or not a water or coolant leak is contaminatingthe engine lubricant EL. In a preferred embodiment, the determination iscarried out by comparing the engine lubricant characteristics to variousthresholds, i.e, perm_slope_limit, temp_slope1_limit, andtemp_slope2_limit. Preferably, water or coolant contamination is deemedto exist if the following three conditions are met: (1)slope1>perm_slope_limit; (2) |slope2|<temp_slope1_limit; and (3)slope3<temp_slope2_limit. Otherwise, if all three are not met, water orcoolant contamination is deemed not to exist. In a preferred embodiment,for example, perm_slope_limit=0.001, temp_slope1_limit=0.37, andtemp_slope2_limit=0.80.

[0091] With respect to the three conditions mentioned above, condition(1) relates to the rate of change of the lubricant's permittivity, andmeeting condition (1) means that the rate of change of the lubricant'spermittivity is excessive or high compared to the threshold level set,perm_slope_limit. This is possibly indicative of water or coolantcontamination. However, permittivity is a temperature dependentcharacteristic or measurement. Accordingly, it is undesirable to relysolely on the rate of change of the lubricant's permittivity which maybe affected by temperature changes, and not truly to due to water orcoolant contamination. To compensate for temperature changes, conditions(2) and (3) must also be met in order for a contamination or leakcondition to be positively identified. Meeting condition (2) indicatesthat the lubricant's temperature is in control and not changing rapidlyor greatly during the period in which the permittivity data wasacquired, i.e., the short term rate of change of the lubricant'stemperature is small relative to the threshold set, temp_slope1_limit.Out of control temperature may be experienced, e.g., when the engine 2is shutting down. Meeting condition (3) indicates that the lubricanttemperature is not ramping up, i.e., the long term rate of change to thelubricant's temperature is below the threshold set, temp_slope2_limit.Excessive temperature ramping may be experienced, e.g., when the engine2 is rapidly advancing through its notches, or the speed of operation israpidly increased.

[0092] By meeting conditions (2) and (3) then, it can be concluded thatany observed changes in the permittivity of the engine lubricant EL overa prescribed level or threshold are attributable to water or coolantcontamination. That is to say, when the immediate temperature is incontrol and it has not been ramping up over time, rising permittivitycan be safely attributed to water or coolant contamination. Accordingly,when condition (1) is also met, a contamination or leak condition isdeemed to exist. In this manner, temperature is compensated for in thedetermination process.

[0093] If a water or coolant leak is deemed to exist at decision step108, then the process 100 branches to step 110 where desired correctiveor otherwise responsive actions are taken. Otherwise, if no-leak isdeemed to exist, the take action step 110 is skipped. Of course, variousactions or combinations or actions may be taken upon the detection of awater/coolant leak. Preferably, the desired actions taken at step 110include one or more of: notifying the engine's operator of the detectedleak, e.g., via the display 52 or other perceivable indicators;communicating the detected leak condition and associated data to theremote site, e.g., via the data link 56; where the detected leak issufficiently serious, automatically shutting down the engine 2, eitherimmediately or within a prescribed time period; scheduling the engine 2for service; exchanging old engine lubricant EL with fresh lubricant FL;etc.

[0094] Next, at decision step 112, it is decided whether or not theprocess 100 should continue. If the process 100 should continue, itbranches back to the acquisition step 104 by way of re-indexing step 114for the next iteration of the process 100. Otherwise, the process 100ends at step 116. Preferably, the process 100 continues automatically aslong as the engine 2 is in operation. Optionally, the process 100 isengaged and/or disengaged as desired by the operator or otherwise,perhaps, via a query or command received from the remote site over thedata link 56.

[0095] If the process 100 is continued, subsequent iterations arecarried out with updated data. The data is preferably updated in there-indexing step 114. With each update the oldest data values used inthe immediately preceding iteration are disregarded, and the remainingother data values are shifted or re-indexed accordingly. Consequently,any newly acquired data values may be placed into the current iterationpositions.

[0096] Please note that the foregoing discussion of the incipientfailure diagnosis 100 preferably relates to railroad applications, i.e.,engines such as those employed in railroad locomotives. Otherapplications are contemplated, such as mining machinery and otheroff-highway vehicles, that use like incipient failure diagnosticprocesses which are tailored to the particular application. For example,in the case of a preferred embodiment for a mine vehicle, the process istailored as follows: rather than using all three lubricantcharacteristics (i.e., slope1, slope2, and slope3) only slope1 andslope2 are used and a substitute third characteristic, the minimumlubricant temperature (nominally termed minT), is used; conditions (1),(2) and (3) are rewritten as slope1>perm_slope_limit,|slope2|<temp_slope1_limit, and minT>temp_mim_limit (i.e., the minimumlubricant temperature is greater than the threshold parametertemp_mim_limit); and the thresholds are set as perm_slope_limit=0.06,temp_slope1_limit=0.25, and temp_min_limit=50° C. Of course, in stillother applications, the incipient failure diagnostic process isoptionally tailored differently for optimum performance therein. In anyevent, the processes similarly compensate for the temperature dependentnature of the permittivity characteristic or measurement. Optionally, avariable diagnostic process is employed which is tunable or tailored tothe particular application in which it operates, or alternately, a fixeddiagnostic process is employed in which the process branches todifferent sub-processes or algorithms based on the application.

[0097] In one preferred alternate embodiment, using the temperaturemeasurements, the corresponding permittivity data values acquired arenormalized to a selected standard temperature based on the temperatureresponse of the sensor. In this way, the permittivity data istemperature compensated, and resulting changes in permittivity over athreshold level may be attributed to water/coolant contamination.

[0098] The time to condemning limit calculation or algorithm is nowdescribed by way of example, with reference to FIG. 5 which is a boxdiagram illustrating the same. Again, this process is alternatelycarried out via software implementation, hardware implementation or acombination of both. The time to condemning limit process is used todetermine the amount of time left until the lubricant quality isdegraded below a predetermined or otherwise selected level. Thisdegradation is consistent with normal operation of the engine 2 and is aconsequence of, e.g., depletion of lubricant additives, ingestion intothe lubricant of foreign materials (i.e., dirt from the surroundingenvironment, wear materials from the engine, and/or blow-by from thecombustion process), break-down of the base stock of the lubricant, etc.In this manner, it is determined how much remaining useful life (RUL)the engine lubricant EL has left.

[0099] The time to condemning limit is based on the monitoredpermittivity of the lubricant EL over time, and is preferably determinedor calculated from hourly medians of the minute permittivity data,nominally termed hourly permittivity data. That is, each consecutive onehour time interval is assigned a permittivity value based on the medianof the minute data for that hour. In turn, based on changes in thehourly permittivity data over time, a determination is made as to theamount of useful life left in the engine lubricant EL.

[0100] The time to condemning limit determination process, which processis generally indicated by reference numeral 200, begins at start box 202where initialization takes place. In addition to optional system,sensor, or other fault checking and/or calibration, initializationpreferably includes the setting of certain parameters includingthresholds and other values used in the time to condemning limitdetermination process 200 such as, e.g., the parameters shift_limit,default_slope, min_data, max_data, m, cond_limit, etc. (describedhereafter). As before, setting of the parameters may be predeterminedand/or fixed and their values optionally stored in one or more of thestorage devices 58 or otherwise. Alternately, the parameter values arevariable, and they may be manually entered, supplied by the remote site,or otherwise selected. In one preferred embodiment, the parameter valuesare obtained from a look-up table or other like source based on theengine type, the lubrication type, and/or other like factors. In anyevent, the assigned parameter values are preferably based on historicalobservations and data related to lubrication degradation. Additionally,the assigned parameter values are preferably set to optimally tune theprocess 200 for specific applications or circumstances.

[0101] The next step 204 is to acquire the hourly permittivity data.Again, the process 200 is iterative and consecutive hourly permittivityvalues are acquired as long as the process or algorithm continues torun. As it is acquired, the data may be stored in one or more of thestorage devices 58. The maximum number of hourly permittivity valuesused in the process 200 is given by max_data, an integer value greaterthan 1. For example, in a preferred embodiment, max_data=168, which is 7days of hourly permittivity data. Max_data defines the largest desiredwindow of hourly permittivity data used in calculating the permittivityslope (described below). Accordingly, as data in excess of max_data isacquired, the oldest acquired data value is disregarded (optionally,deleted or written over), the remaining values re-indexed accordingly,and the newly acquired data value is placed in the current iterationposition.

[0102] Next, at decision step 206, it is determined if the lubricant hadbeen changed or significantly topped-off recently. This is preferablyaccomplished by looking for jumps or shifts in the hourly permittivitydata which exceed a predetermined or otherwise selected threshold,shift_limit. That is, when the difference between hourly permittivitydata from adjacent acquisitions exceeds the shift_limit, it indicatesthat the lubricant was changed or significantly topped-off between thoseacquisitions. For example, in one preferred embodiment,shift_limit=0.035 permittivity units.

[0103] The change or top-off is deemed to be sufficiently recent if lessthan a certain threshold number of acquisitions have been made since themost recent top-off or change. This threshold is nominally given asmin_data, where min_data is an integer number less than max_data. Forexample, in one preferred embodiment, min_data=72, which is 3 days ofhourly permittivity data. In this manner, min_data defines the smallestdesired window of hourly permittivity data used in calculating thepermittivity slope (described below). Accordingly, if the differencebetween any two adjacently acquired hourly permittivity values withinthe min_data most recently acquired values is greater than shift_limit,then a lubrication change or significant top-off is deemed to haverecently occurred, otherwise no lubrication change or significanttop-off is deemed to have recently occurred.

[0104] If at decision step 206, a change or significant top-off isdeemed to have recently occurred, the process 200 branches to step 208,otherwise the process continues on to step 210. At step 208, thepermittivity slope, perm_slope, is set to a default value,default_slope. For example, in one preferred embodiment,default_slope=0.0004. The permittivity slope as use here isrepresentative of the rate of over-all quality degradation for thelubricant. The permittivity slope is set to the default value when thereis insufficient hourly permittivity data acquired since the last changeor top-off to reliably determine the actual rate of over-all qualitydegradation for the engine lubricant EL. Accordingly, it is assumed tobe the default rate and so set at step 208. On the other hand, if thereis sufficient hourly permittivity data acquired since the last change ortop-off to reliably determine a rate of over-all quality degradation, itis done so at step 210.

[0105] If the number of acquisitions since the last lubricant change orsignificant top-off is greater than max_data, then the max_data mostrecent hourly permittivity values are used to calculate the permittivityslope, otherwise all the hourly permittivity values since the lastlubricant change or significant top-off are used to calculate thepermittivity slope. Note, in the latter case, there are at leastmin_data hourly permittivity values used in the slope calculation. Thatis to say, the hourly permittivity values within a sampling window areused to determine the permittivity slope, where the window has a maximumwidth of max_data and a minimum width of min_data. The window extendsfrom the most recently acquired hourly permittivity value back to themost recent lubrication change or significant top-off or alternatelyback to the max_data width, which ever is smaller,. In any event, thepermittivity slope is then preferably calculated by averaging thedifferences between adjacent hourly permittivity values within thewindow. With each new or updated acquisition or iteration, the windowslides forward by one hourly permittivity value.

[0106] Optionally, the data in the window is filtered or conditionedprior to calculating or otherwise determining the permittivity slope instep 210. In one preferred embodiment, a portion of the data havingextreme values is disregarded for purposes of the permittivity slopecalculation. For example, when the hourly permittivity data is sorted byvalue from highest to lowest or vice versa, 10% of the data on both endsthereof may be discarded or otherwise not considered for purposes of thepermittivity slope calculation. In this manner, extreme and potentiallyanomalous data does not influence the permittivity slope determination.

[0107] After the permittivity slope has been calculated in step 210 orset to the default value in step 208, the time to condemning limit,time_to_cond_limit, is determined or calculated at step 212.Mathematically, the time to condemning limit is preferably calculated asfollows: if the current permittivity is less then the condemning limit,then: $\begin{matrix}{{{{time\_ to}{\_ cond}{\_ limit}} = \frac{{cond\_ limit} - {current\_ perm}}{perm\_ slope}};} & (2)\end{matrix}$

[0108] otherwise:

time_to_cond_limit=0  (3);

[0109] where, time_to_cond_limit represents a determination of the timeremaining until the condemning limit is reached; cond_limit is thecondemning limit, a parameter representing the permittivity of thelubricant when it has reached its condemning limit (i.e., when it hasreached the end of its useful life); current_perm represents the currentpermittivity of the engine lubricant EL; and, perm slope represents thepreviously determined permittivity slope or rate of quality degradationfor the engine lubricant EL, be it default or calculated.

[0110] Preferably, the current permittivity, current_Perm, is taken asthe median of the m most recently acquired hourly permittivity values,where m is an integer number greater than 1 and less than min_data. Forexample, in one preferred embodiment, m=4. Optionally, if there has beena lubricant change or significant top-off within the time period of them most recently acquired hourly permittivity values, less than m datavalues may be used to determine the current permittivity. Alternately,the time to condemning limit calculation may be postponed until at leastm hourly permittivity data values have been acquired since the lastlubrication change or significant top-off.

[0111] Based on the time to condemning limit as determined in step 212,at decision step 214 it is determined if any desired actions are to betaken. For example, depending upon how low the time to condemning limitis, particular actions are taken. In one preferred embodiment, if thetime to condemning limit is less than or equal to 5 days for a railroadlocomotive or less then or equal to 2 days for other off-highwayvehicles, then optionally this information is communicated via the datalink 56 to the remote location. If an action is to be taken, then theprocess 200 branches to step 216 where desired corrective or otherwiseresponsive actions are taken. Otherwise, if no action is to be taken,step 216 is skipped. Of course, various actions or combinations oractions may be taken as desired. Preferably, the desired actions takenat step 216 include one or more of: notifying the engine's operator ofthe time to condemning limit, e.g., via the display 52 or otherperceivable indicators; communicating the time to condemning limit andassociated data to the remote site, e.g., via the data link 56; wherethe detected leak is sufficiently low, e.g., at or near zero,automatically shutting down the engine 2, either immediately or withinthe time period before the condemning limit is reached; scheduling theengine 2 for service; exchanging old engine lubricant EL with freshlubricant FL; etc.

[0112] Next, at decision step 218, it is decided whether or not theprocess 200 should continue. If the process 200 should continue, itbranches back to the acquisition step 204 by way of re-indexing step 220for the next iteration of the process 200. Otherwise, the process 200ends at step 222. Preferably, the process 200 continues automatically aslong as the engine 2 is in operation. Optionally, the process 200 isengaged and/or disengaged as desired by the operator or otherwise,perhaps, via a query or command received from the remote site over thedata link 56. If the process 200 is continued, subsequent iterations arecarried out with updated data. The data is preferably updated in there-indexing step 220. With each update the oldest data values used inthe immediately preceding iteration are disregarded if they are nolonger going to be employed, and the remaining other data values areshifted or re-indexed accordingly. Consequently, any newly acquired datavalues may be placed into the current iteration positions.

[0113] Again, with respect to the diagnostic cell 27, at least one ofthe sensors 28 incorporated therein is preferably a dynamic (rotational)viscocometer or other like viscosity sensor which obtains measurementsrelated to the viscosity of the lubricant EL. With use, a lubricant'sviscosity will generally tend to increase slowly in the absence of an“abnormal” event. This is due to the build-up over time of soot,insoluble oxidation products and/or other combustion byproducts in thelubricant. In this manner, viscosity is related to the quality of thelubricant. An observed increase in viscosity is indicative of qualitydegradation. This is particularly true for mono-grade lubricants, i.e.,lubricants absent viscosity modifiers. Accordingly, in a preferredembodiment of the present invention, the engine lubricant quality istracked in part by monitoring changes in the viscosity of the lubricantEL. A time to condemning limit for the engine lubricant EL is thenpredicated on the viscosity monitoring.

[0114] The condemning limit is the point at which the lubricant qualityis deemed to have degraded to an unacceptably low level. Theunacceptably low level is preferably defined as the level at which thelubricant is no longer sufficiently useful for one or more of itsintended purposes, e.g., protecting against engine wear. When thelubricant's viscosity reaches a predetermined or otherwise selectedvalue, it is deemed to have met the condemning limit. The time tocondemning limit is therefore an indication or otherwise representativeof the RUL in the lubricant.

[0115] Additionally, in a preferred embodiment, fuel contamination ofthe lubricant is diagnosed or detected based upon viscosity data, and aswith degradation due to soot and/or combustion byproduct built-up, atime to condemning limit based on degradation due to fuel contaminationis also determined. Contrary to the case of degradation due to sootand/or combustion byproduct build-up, however, lubricant degradation dueto fuel contamination is marked by a decrease in viscosity.

[0116] Determining the time to condemning limit in either case, allowsthe operator, maintenance personnel or other interested parties to beadvised as to the amount of time remaining before the unacceptablequality level is reached. They are therefore able to plan accordingly,and take desired corrective or otherwise responsive actions prior toexceeding the condemning limit. Likewise, by detecting for fuelcontamination, lubricant failure and/or the attendant consequences ofexcessive lubricant degradation caused thereby are avoidable. Thedesired corrective or otherwise responsive actions selectively takeninclude, e.g., in an urgent or extreme case, shutting-down of the engine2, scheduling and/or performing engine service including a lubricationchange, adding fresh lubricant FL from the reservoir 40, or removingused engine lubricant EL and routing it to the reservoir 32, ifavailable. In this manner then, the engine 2 is protected from thehazards of lubricant failure and/or degradation while maximizing theengine's operation time between servicing by precisely determining theappropriate time for the next service stop.

[0117] As with the permittivity, the viscosity is a temperaturedependent characteristic of the engine lubricant EL. Accordingly, thetemperature sensor is also preferably included among the sensors 28incorporated in the diagnostic cell 27 to take measurements of theengine lubricant's temperature concurrently with each viscositymeasurement.

[0118] The viscosity based diagnostic process in accordance with apreferred embodiment of the present invention is now described by way ofexample, with reference to FIG. 6 which is a box diagram illustratingthe same. The diagnostic process is alternately carried out via softwareimplementation, hardware implementation or a combination of both.

[0119] The diagnostic process, which is generally indicated by referencenumeral 300, begins at start box 302 where initialization takes place.In addition to optional system, sensor, or other fault checking and/orcalibration, initialization preferably includes the setting of certainconfigurable parameters including thresholds and other values used inthe diagnosis 300 such as, e.g., the parameters a, b,calibration_constant, n, m, N, visc_lower1, visc_lower2,visc_lower_limit, visc_upper, and visc upper_limit (describedhereafter). Setting of the parameters may be predetermined and/or fixedand their values optionally stored in one or more of the storage devices58 or otherwise. Alternately, the parameter values are variable, andthey may be manually entered, supplied by the remote site, or otherwiseselected. In one preferred embodiment, the parameter values are obtainedfrom a look-up table or other like source based on the engine type, thelubrication type, and/or other like factors. In any event, the assignedparameter values are preferably based on historical observations anddata associated with the relationship between lubricant viscosity andquality degradation and/or fuel contamination. Additionally, theassigned parameter values are preferably set to optimally tune thediagnostic process 300 for specific applications or circumstances.

[0120] The next step 304 is to acquire a set of measurements or data.The diagnostic process 300 is preferably a continually updated iterativeprocess with each iteration employing a set of data values representingthe most recent viscosity data and the most recent temperature data.Alternately, each data point may represent an individual measurement oran average or otherwise weighted measurement taken over time. In apreferred embodiment, the acquired data is minute data. Minute data forconsecutive 1 minute periods is acquired approximately concurrently forboth viscosity and temperature. A complete data set acquisition for agiven iteration preferably includes obtaining an hour's worth ofviscosity values and temperature values. With each successive iteration,the next hour's worth of viscosity data and temperature data isacquired. In this case, the diagnosis is updated hourly.

[0121] As it is acquired, the data may be stored in one or more of thestorage devices 58. Once enough data has been acquired, the diagnosticprocess 300 may continue. In the beginning of the diagnostic process300, there may be a certain initial latency period before enough datahas been acquired to carry out all the desired calculations and/ordeterminations. Thereafter, subsequent iterations are carried out inaccordance with each acquisition of the next hour's viscosity data andcorresponding temperature data. With each update the oldest hour of datavalues used in the immediately preceding iteration are now disregarded,the remaining other hours of data values are shifted or re-indexedaccordingly, and the newly acquired hour of data values placed into thecurrent iteration positions. Optionally, to conserve storage room, theoldest disregarded data set in one or more of the storage devices 58 isdiscarded, deleted or written over. Alternately, it is saved forhistorical analysis, record keeping purposes, or the like.

[0122] In a preferred embodiment of the present invention, there is alinear relationship between the load experienced by the rotationalviscometer's motor and the viscosity of the lubricant being monitored.Accordingly, the viscosity measurement is preferably calculated ordetermined from the viscometer's motor load using a calibration constantwhich is configurable parameter. This can be mathematically representedas follow:

Viscosity=motor_load*calibration_constant  (4);

[0123] where, viscosity represents the measured viscosity, motor_loadrepresents the load on the viscometer's motor, and calibration_constantrepresents the configurable parameter. Preferably, the viscometer isre-referenced periodically, e.g., once per year, by taking severallubricant samples from the engine 2 and analyzing them with anindependent second viscometer or other like viscosity measuring sensor.If the original viscoineter has experienced drift, then this shall becorrected via a configurable viscosity drift parameter.

[0124] As the viscosity will vary with temperature, the viscosity datais normalized to a common reference temperature. Temperaturecompensation is preferably carried out using two compensation constantswhich are also configurable parameters. The common reference temperatureis preferably set to 100° C., because for various lubricant viscositygrades, minimum viscosity specifications are set at this temperature.Mathematically, the relationship between viscosity and temperature is ofthe following form:

log(log(viscosity))=a*log(temperature)+b  (5);

[0125] where, viscosity is in centipoise, temperature is in Kelvin, arepresents the viscosity-temperature slope, and b represents theviscosity intercept.

[0126] The determination and/or setting of configurable parameters ispreferably carried out at start up 302. However, a and b, can vary withlubrication type and viscosity grade. Therefore, the diagnostic process300 will optionally detect and/or determine when to re-calibrateparameters a and b by monitoring the variation of temperaturecompensated viscosity in relation to temperature over short time periodswhere the true viscosity is assumed to be constant. Initially the a andb values are read from configurable parameters, but are recalculateperiodically, as necessary, or as otherwise desired. This information isoptionally downloaded from time to time to the remote site over the datalink 56 along with a flag indicating that the viscometer normalizationequation (5) was re-calculated.

[0127] In a preferred embodiment, the viscosity normalized to the commonreference temperature of 100° C. is calculated or otherwise determinedfrom the measured viscosity obtained at the measured temperature.Mathematically, this is done by using the above equation (5) rearrangedinto the following form: $\begin{matrix}{{\log \left( {{\log \left( {{viscosity}\quad 100} \right)} = {\log \left( {\log \quad {viscosity}} \right)}} \right)} - {a*\left( {{{\log \left( {{temperature}/373.16} \right)};{or}},} \right.}} & (6) \\{{{viscosity}\quad 100} = {\exp\left( {\exp\left( {{{\log ({viscosity})} - {a*\left( {\log \left( {{temperature}/373.16} \right)} \right)}};} \right.} \right.}} & (7)\end{matrix}$

[0128] where, viscosity100 represents the viscosity normalized to thecommon reference temperature of 100° C., viscosity represents themeasured viscosity, temperature represents the corresponding measuredtemperature in degrees Kelvin, and degrees Kelvin=degreesCentigrade+273.16.

[0129] Accordingly, in a preferred embodiment, for each iteration of thediagnostic process 300, the acquisition step 304 involves theacquisition of an hour's worth of viscosity100 minute data andcorresponding temperature minute data. That is, 60 consecutiveviscosity100 data values and 60 corresponding temperature data values.

[0130] At the next step 306, “hourly” viscosity data is generated fromeach consecutive hour's worth of acquired minute data. The hourlyviscosity data is an optionally weighted value representing theviscosity100 data for that hour. Preferably, the hourly viscosity datais the median of the minute data for that hour, and it is termed thehourly viscosity median. Additionally, it is preferred that certainacquired minute data not be included in calculating or determining thehourly viscosity median. In particular, minute data which was acquiredwith a corresponding temperature below a predetermined or otherwiseselected temperature threshold, e.g., less than 40° C., is notconsidered when calculating the hourly viscosity median. It is possiblethen that the hourly viscosity median is calculated with less than 60data values. However, if the number of values is not above some minimumthreshold, e.g., 20 values, then no median is calculated for that hour.In this manner, if there is an insufficient amount of reliable data inany given hour, then the data for that hour is not used.

[0131] The hourly viscosity data values are preferably stored in one ormore of the storage devices 58 from which they are selectively accessed.With each iteration, the hourly viscosity data is updated. That is, theoldest value previously used which is no longer going be used in thediagnostic process 300 is disregarded (optionally, deleted or otherwisediscarded), the remaining values are re-indexed or shifted overaccordingly, and the newly generated hourly viscosity data value enteredinto the current iteration position. In this manner, the hourlyviscosity data is updated each hour.

[0132] At step 308, slope computations are made based on the hourlyviscosity data. Preferably, a number n of the most recently establishedor generated hourly viscosity data values are used for the slopecomputations, where n is a integer value greater 1. Preferably, n=12. Ina preferred embodiment, the algorithm or calculation used to determinethe slope is mathematically given by: $\begin{matrix}{{{slope} = \frac{{n{\sum\limits_{i = 1}^{n}{x_{i}y_{i}}}} - {\underset{i = 1}{\overset{n}{\sum\quad}}x_{i}{\sum\limits_{i = 1}^{n}y_{i}}}}{{n{\sum\limits_{i = 1}^{n}x_{i}^{2}}} - {n\left\lbrack {\sum\limits_{i = 1}^{n}x_{i}} \right\rbrack}^{2}}},} & (8)\end{matrix}$

[0133] where slope represents the rate of change of the respective datavalues, n represents the total number of data points or values used inthe calculation, x_(i) represents the integers from 1 to n, and y_(i)represents the respective data values for the calculation, i.e., thehourly viscosity data or medians.

[0134] Preferably, after each update of the hourly viscosity data, theslope is re-calculated using the updated hourly viscosity data.Accordingly, the slope is also iteratively updated. A number m of themost recently calculated slope values are preferably retained forsubsequent use, where m is an integer greater than 1. As with n,preferably, m=12. In this manner then, m slopes are generated, updatedhourly, with each slope being calculated on the immediately preceding nhourly viscosity data values. These collective slope values arenominally termed, for purposes herein, the “m n-hour slopes.” Based onthe m n-hour slopes and the hourly viscosity data, it is determined atdecision step 310 if any of four separate sets of conditions are met.When a set of conditions is met, a desired action in response thereto istaken at step 312, after which a time to condemning limit is calculatedor determined at step 314, otherwise, the take action step 312 isbypassed.

[0135] The conditions have a number of associated thresholds and limitswhere are define here for the sake of convenience. Listed here inrelative order from lowest value to highest value, the thresholds andlimits preferably are as follows: visc_lower_limit is the lowerviscosity condemning limit for the lubricant; visc_lower2 is a secondlower threshold; visc_lower1 is a first lower threshold; visc_upper isan upper threshold; and visc_upper_limit is the upper viscositycondemning limit for the lubricant.

[0136] It is generally desirable for the viscosity of an SAE 40 or 20W40lubricant utilized in locomotive applications at 100° C. to fall between12.5 and 16.5 centistoke (10.5 and 16.0 centipoise (cP)). However,viscosity specifications for lubricating oils used in variousapplications and/or engines may vary. Accordingly, in one preferredembodiment, the aforementioned limits and thresholds are assigned valuesas follows: visc_lower_limit=10.5 cP; visc_lower2=11.75 cP;visc_lower1=12.0 cP; visc_upper=16.0 cP; and visc_upper_limit=16.75 cP.

[0137] With respect to the four sets of conditions mentioned above, thefirst set of conditions is aimed at detecting or indicating a fuel leakor fuel contamination of the lubricant EL. This set of conditions ispreferably given as follows: if each of the m n-hour slopes is less thanzero, and the current hourly viscosity data value is less thanvisc_lower1, then a fuel leak is deemed to exist and the time tocondemning limit is given by: time_to_cond_limit=(visc_lower_limit−thecurrent hourly viscosity median)/the minimum of the m n-hour slopes.

[0138] The second set is aimed at detecting or indicating a slow fuelleak or minor fuel contamination of the engine lubricant EL. The secondset preferably includes a single condition, given as follows: if each ofthe most recent N hourly viscosity medians is less than visc_lower2,then a slow fuel leak is deemed to exist and the time to condemninglimit is given by: time_to_cond_limit=(visc_lower_limit−the maximumviscosity data value for the current hour)/an N-hour slope. Theconfigurable parameter N is an integer number greater than n.Preferably, N=2n, or 24. Similarly, the N-hour slope is the slopecalculated via equation (8) using the N most recently generated hourlyviscosity data values.

[0139] The third set of conditions is aimed at detecting when orindicating that there is no fuel leak or fuel contamination of theengine lubricant EL. This set of conditions is preferably given asfollows: if the current hourly viscosity data value is greater thanvisc_lower1 and less than visc_upper then a fuel leak is deemed not toexist. In this case, the time to condemning limit is determined based onan average of the m n-hour slopes. If the average is less than zero,then time_to_cond_limit=(visc_lower_limit−the maximum viscosity datavalue for the current hour)/the average, otherwise if the average isgreater than zero, then time_to_cond_limit=(visc_upper_limit−the maximumviscosity data value for the current hour)/the average.

[0140] Finally, the fourth set of conditions is aimed at detecting whenor indicating that soot and/or other byproduct build-up hassignificantly degraded the quality of the lubricant to a point where theupper viscosity condemning limit is being approached. This set ofconditions is preferably given as follows: if each of the m n-hourslopes is greater than zero, and the current hourly viscosity data valueis greater than visc_upper, then significant quality degradation isdeemed to exist and the time to condemning limit is given by:time_to_cond_limit=(visc_upper_limit−the current hourly viscositymedian)/the maximum of the m n-hour slopes.

[0141] In this manner then, the quality or amount of degradation of theengine lubricant EL is determined and/or diagnosed. The degree/level orexistence of fuel contamination is also determined and/or diagnosed.Moreover, the diagnostic accuracy is improved insomuch as these goalsare achieved via monitoring of the actual physical characteristic orproperties of the engine lubricant itself. Additionally, the temperaturedependant nature of the viscosity data or measurements is compensatedfor in the diagnosis.

[0142] Of course, various actions or combinations or actions may betaken at the take action step 312 depending upon the diagnosis.Preferably, the desired actions taken at step 312 include one or moreof: notifying the engine's operator of a detected fuel leak or of thedegree of a fuel leak or of the time until a condemning limit isreached, e.g., via the display 52 or other perceivable indicators;communicating the detected leak condition or time to condemning limitand associated data to the remote site, e.g., via the data link 56;where the detected leak is sufficiently serious or time to condemninglimit sufficiently small, automatically shutting down the engine 2,either immediately or within a prescribed time period or within the timeperiod before the condemning limit is reached; scheduling the engine 2for service; exchanging old engine lubricant EL with fresh lubricant FL;etc.

[0143] Next, at decision step 316, it is decided whether or not thediagnostic process 300 should continue. If the process 300 shouldcontinue, it branches back to the acquisition step 304 by way ofre-indexing step 318 for the next iteration of the process 300.Otherwise, the process 300 ends at step 320. Preferably, the process 300continues automatically as long as the engine 2 is in operation.Optionally, the process 300 is engaged and/or disengaged as desired bythe operator or otherwise, perhaps, via a query or command received fromthe remote site over the data link 56.

[0144] If the process 300 is continued, subsequent iterations arecarried out with updated data. The data is preferably updated in there-indexing step 314. With each update the oldest data values used inthe immediately preceding iteration are disregarded, and the remainingother data values are shifted or re-indexed accordingly. Consequently,any newly acquired data values may be placed into the current iterationpositions.

[0145] Please note that the foregoing discussion of the diagnosticprocess 300 preferably relates to railroad applications, i.e., enginessuch as those employed in railroad locomotives. Other applications arecontemplated, such as mining machinery and other off-highway vehicles,that use like diagnostic processes which are tailored to the particularapplication. Of course, in other applications, the diagnostic process isoptionally tailored differently for optimum performance therein. In anyevent, the processes similarly compensate for the temperature dependantnature of the viscosity characteristic or measurement. Optionally, avariable diagnostic process is employed which is tunable or tailored tothe particular application in which it operates, or alternately, a fixeddiagnostic process is employed in which the process branches todifferent sub-processes or algorithms based on the application.

[0146] In a preferred embodiment, the time to condemning limitdetermination process 200, the water/coolant leak detection process 100and the viscosity based diagnosis 300 are carried out or runsimultaneously with each other and/or other optional diagnosticprocesses which monitor lubricant quality, level, etc. In which case,the data and/or measurements collected from the sensors 28 which arecommon to multiple processes may be shared. Likewise, the start and endsteps may be coincident, and, in fact, there may be a single start and asingle end process which act as the start and end steps for multipleprocesses. Alternately, one or more of the processes are completelyindependent.

[0147] In short, the invention has been described with reference to thepreferred embodiments. Obviously, modifications and alterations willoccur to others upon reading and understanding the preceding detaileddescription. It is intended that the invention be construed as includingall such modifications and alterations insofar as they come within thescope of the appended claims or the equivalents thereof.

Having thus described the preferred embodiments, the invention is nowclaimed to be:
 1. A method of monitoring a lubricant, said methodcomprising: (a) measuring the lubricant's temperature; (b) measuring thelubricant's permittivity; (c) compensating for temperature dependence inthe permittivity; and, (d) determining if the lubricant has beencontaminated by a coolant.
 2. The method according to claim 1, saidmethod further comprising: determining a rate of change of thelubricant's permittivity for a first period of time; and, determining arate of change of the lubricant's temperature for a second period oftime; wherein the lubricant is determined to be contaminated by acoolant if the rate of change of the lubricant's permittivity for thefirst period of time is greater than a first threshold, and an absolutevalue of the rate of change of the lubricant's temperature for thesecond period of time is less than a second threshold.
 3. The methodaccording to claim 2, wherein the first and second periods of time arethe same periods of time.
 4. The method according to claim 3, saidmethod further comprising: determining a rate of change of thelubricant's temperature for a third period of time, said third period oftime being greater than the first and second periods of time; whereinfor a determination to be made that the lubricant is contaminated by acoolant, it has to also be found that the rate of change of thelubricant's temperature for the third period of time is less than athird threshold.
 5. The method according to claim 3, said method furthercomprising: selecting a minimum temperature from those used to determinethe rate of change of the lubricant's temperature for the second timeperiod; wherein for a determination to be made that the lubricant iscontaminated by a coolant, it has to also be found that the minimumtemperature is greater than a threshold temperature.
 6. A method ofmonitoring a lubricant, said method comprising: (a) obtaining, overtime, permittivity data from measured permittivity values of thelubricant; (b) determining a rate of degradation of the lubricant'squality based on changes in the permittivity data over time; and, (c)determining an amount of time until the lubricant reaches a set degradedquality level.
 7. The method according to claim 6, said method furthercomprising: determining if the lubricant has been changed or topped-offby detecting changes in the permittivity data which exceed a thresholdlevel.
 8. The method according to claim 6, wherein the amount of timeuntil the lubricant reaches the set degraded quality level is given by:(cond_limit−current_perm)/perm_slopewhere, cond_limit represents acondemning limit defined by the lubricant's permittivity when thelubricant has reach the set degraded quality level; current_permrepresents the lubricant's current determined permittivity; andperm_slope represents the determined rate of degradation of thelubricant's quality based on changes in the permittivity data.
 9. Themethod according to claim 8, wherein the current determined permittivityof the lubricant is a median of a plurality of most recently obtainedpermittivity data.
 10. A lubrication system for an engine, saidlubrication system comprising: a lubricant; and, a diagnostic cell whichsamples the lubricant for diagnostic testing thereof, said cellincluding; a permittivity sensor which monitors the lubricant'spermittivity; and, a temperature sensor which monitors the lubricant'stemperature.
 11. The lubrication system according to claim 10, whereinsaid diagnostic cell further includes: a manifold in which thepermittivity and temperature sensors are mounted, said manifold beingarranged such that sampled lubricant is selectively made to encounterthe permittivity and temperature sensors.
 12. The lubrication systemaccording to claim 10, further comprising: a controller which interfaceswith the diagnostic cell to carry out the diagnostic testing, saidcontroller receiving permittivity data from the permittivity sensor andtemperature data from the temperature sensor.
 13. The lubrication systemaccording to claim 12, wherein the diagnostic testing carried outincludes determining if the lubricant has been contaminated by acoolant.
 14. The lubrication system according to claim 13, wherein thecontroller determines a rate of change of the lubricant's permittivityfor a first time period based on the permittivity data it receives, andthe controller determines a rate of change of the lubricant'stemperature for a second time period based on the temperature data itreceives, such that the controller determines that the lubricant hasbeen contaminated by a coolant if the rate of change of the lubricant'spermittivity for the first time period is greater than a first thresholdand an absolute value of the rate of change of the lubricant'stemperature for the second time period is less than a second threshold.15. The lubrication system according to claim 14, wherein the first andsecond time periods are the same.
 16. The lubrication system accordingto claim 15, wherein the controller further determines a rate of changeof the lubricant's temperature for a third time period based on thetemperature data it receives, said third time period being longer thanthe first and second time periods, such that for the controller todetermine that the lubricant has been contaminated by a coolant, thecontroller has to also find that the rate of change of the lubricant'spermittivity for the third time period is less than a third threshold.17. The lubrication system according to claim 15, wherein the controllerfurther determines a minimum lubricant temperature for the second timeperiod from the temperature data it receives, such that for thecontroller to determine that the lubricant has been contaminated by acoolant, the controller has to also find that the minimum lubricanttemperature is greater than a threshold temperature.
 18. The lubricationsystem according to claim 12, wherein the controller determines a timeto condemning limit for the lubricant based on the permittivity datareceived.
 19. The lubrication system according to claim 18, wherein thetime to condemning limit is given by:(cond_limit−current_perm)/perm_slope where, cond_limit represents acondemning limit defined by the lubricant's permittivity when thelubricant has reach a selected level of degradation; current_permrepresents the lubricant's current determined permittivity; andperm_slope represents a rate of lubricant quality degradation asdetermined from the permittivity data.
 20. The lubrication systemaccording to claim 10, wherein the engine is selected from the groupconsisting of a railroad locomotive engine, and a mining vehicle engine.21. A method of monitoring a lubricant, said method comprising the stepsof: (a) obtaining measurements of the lubricant's viscosity; (b)obtaining measurements of the lubricant's temperature; (c) normalizingthe viscosity measurements based on the temperature measurements suchthat the normalized viscosity measurements all relate to a commonreference temperature; and, (d) diagnosing a condition of the lubricantbased on the normalized viscosity measurements.
 22. The method accordingto claim 21, wherein step (d) comprises: diagnosing fuel contaminationof the lubricant based on the normalized viscosity measurements.
 23. Themethod according to claim 22, wherein step (d) further comprises:distinguishing between different degrees of fuel contamination based onthe normalized viscosity measurements.
 24. The method according to claim22, said method further comprising: (e) determining, based on thenormalized viscosity measurements, a time to condemning limit for thelubricant due to fuel contamination.
 25. The method according to claim21, wherein step (d) comprises: diagnosing quality degradation of thelubricant based on the normalized viscosity measurements.
 26. The methodaccording to claim 25, said method further comprising: (e) determining,based on the normalized viscosity measurements, a time to condemninglimit for the lubricant due to quality degradation.
 27. The methodaccording to claim 21, said method further comprising: (e) determining,based on the normalized viscosity measurements, a time to condemninglimit for the lubricant.
 28. The method according to claim 27, whereinthe time to condemning limit is selected from the group consisting of:an upper viscosity limit under which it is desired that the lubricant'sviscosity remain, and a lower viscosity limit over which it is desiredthat the lubricant's viscosity remain.
 29. A lubrication system for anengine, said lubrication system comprising: a lubricant; a diagnosticcell which samples the lubricant for diagnostic testing thereof, saidcell including; a viscosity sensor which monitors the lubricant'sviscosity; and, a temperature sensor which monitors the lubricant'stemperature; and, a controller which interfaces with the diagnostic cellto carry out the diagnostic testing, said controller receiving viscositydata from the viscosity sensor and temperature data from the temperaturesensor, wherein the viscosity and temperature data is processed todiagnose a condition of the lubricant.
 30. The lubrication systemaccording to claim 29, wherein the condition diagnosed is selected fromthe group consisting of fuel contamination of the lubricant, and qualitydegradation of the lubricant.
 31. The lubrication system according toclaim 29, wherein the viscosity data and the temperature data areprocessed to determine a time to condemning limit for the lubricant. 32.The lubrication system according to claim 29, wherein the viscositysensor is a dynamic viscometer.
 33. The lubrication system according toclaim 29, further comprising: a data link which transfers data betweenthe lubrication system and a site remote from the lubrication system.34. The lubrication system according to claim 29, further comprising: amanifold in which the viscosity and temperature sensors are mounted,said manifold being arranged such that sampled lubricant is selectivelymade to encounter the viscosity and temperature sensors.
 35. Thelubrication system according to claim 29, further comprising: indicatingmeans for providing a human perceivable indication of the condition ofthe lubricant.
 36. The lubrication system according to claim 29, furthercomprising: a storage device in which the viscosity and temperature dataare saved.
 37. The lubrication system according to claim 29, furthercomprising: lubricant refreshing means for selectively carrying out oneor more functions in response to the diagnosed condition of thelubricant, said functions being selected from the groups consisting of:removing lubricant from the lubrication system, and adding freshlubricant to the lubrication system.
 38. The lubrication systemaccording to claim 29, wherein the engine is selected from the groupconsisting of a railroad locomotive engine, and a mining vehicle engine.